The property in Wickford, Essex, where Ryan Cleary was arrested as part of a Scotland Yard and FBI probe into LulzSec

A note left on the front door of the Essex property where Ryan Cleary was arrested

A British teenager suspected of masterminding a global computer hacking plot from his bedroom could face a fight against extradition to the US.

Ryan Cleary was arrested at his detached family home in Essex as part of a Scotland Yard and FBI probe into LulzSec, a group claiming responsibility for hacking attempts on the UK's Serious Organised Crime Agency, the US Senate and the CIA.

Neighbours who witnessed the dawn police swoop spoke of their shock as the "very bright" 19-year-old university student was questioned.

Detectives believe Cleary was a "major player" with LulzSec, which has also claimed security breaches at games firms Nintendo and Sony.

As American authorities were kept closely informed over the "pre-planned intelligence-led operation", lawyers said US prosecutors may demand he faces justice across the Atlantic.

Mark Spragg, an extradition lawyer at London-based firm Keystone Law, said: "If the charges on which he was arrested would result in a sentence in excess of 12 months, then potentially it would constitute an extradition offence."

LulzSec is said to have established itself as a formidable splinter group to Anonymous, the hacking group embroiled in the WikiLeaks fallout.

The group was believed to have initially targeted only US broadcasters, including PBS and Fox, and gaming firms.

But the Twitter page @LulzSec recently declared its intention to break into government websites and leak confidential documents.

Soca, the UK national law enforcement unit dubbed the British FBI, was forced to temporarily take its website off-line on Monday after LulzSec bombarded it with traffic to stop other users accessing it.